In a magnetic position detection device, a Hall element, a magnetoresistive element, or the like is used as a magnetosensitive element. In many cases, the magnetosensitive element is arranged so as to be opposed to a magnetic encoder including N-magnetic poles and S-magnetic poles that are alternately arranged at a constant pitch of λ/2 (λ: pitch of one magnetic-pole pair (N-pole and S-pole)). In this case, when the magnetic encoder and the magnetosensitive element move relative to each other, a magnetic field applied to the magnetosensitive element varies to change an output of the magnetosensitive element. The change in output of the magnetosensitive element at this time is read, thereby being capable of detecting a relative position between the magnetic encoder and the magnetosensitive element.
As an example of application of the above-mentioned detection method, detection of an electrical angle, which is required for rotation control for a brushless motor, is given. The “electrical angle” is an angular position when a rotation angle corresponding to one pair of N-pole and S-pole of the motor is 360°. In this application, the electrical angle of 360° of the motor is defined as one period. Two systems of the magnetosensitive elements, which have outputs that change in a sinusoidal fashion with respect to the electrical angle and have phases different from each other by 90°, are arranged. An arc tangent of the outputs of the two systems is computed, thereby detecting the electrical angle.
The following is known about a direction detection type magnetoresistive element having a resistance value that changes depending on a magnetic-field direction as disclosed in Patent Literature 1. Specifically, when being operated in a saturation magnetic field, the magnetoresistive element is insensitive to noise generated by fluctuation in magnetic-field intensity, and reacts only to the magnetic-field direction without increasing or decreasing the resistance value depending on the fluctuation in magnetic-field intensity due to a variation in magnetic GAP (clearance), temperature characteristics of a magnet, and the like, to thereby exhibit extremely stable detection performance. Therefore, when the direction detection type magnetoresistive element is used for motor control, the detection of the electrical angle with high stability can be realized.